1. Field of the Invention
The field of art to which the present invention pertains is catalytic isomerization of dimethylnapthalenes. Relevant U.S. classifications where art may be found include U.S. Class 260-668(a) or 668(f).
2. Description of the Prior Art
U.S. Pat. No. 3,806,552 issued Apr. 23, 1974, relates to the vapor phase isomerization of dimethylnaphthalenes using a catalyst comprising 65 to 95 percent by weight of a hydrogen form of mordenite in which about 80 percent by weight of the metal cations are replaced with hydrogen ions, and 35 to 45 percent by weight of an assistant catalyst selected from the group consisting of bentonite and fuller's earth.
Japanese Pat. No. 75 0059-357 issued May 22, 1975, relates to the isomerization of dimethylnaphthalenes by contacting a feed material with a mordenite catalyst containing one or more metals of chromium, molybdenum, and tungsten.
Japanese Pat. No. 75 0059-356 issued May 22, 1975, relates to the isomerization of dimethylnaphthalenes by contacting a feed mixture with a mordenite catalyst containing one or more ions of arsenic, bismuth, and antimony.
Japanese patent application No. 45-125543 filed Dec. 29, 1970, published Nov. 29, 1972, relates to isomerization of dimethylnaphthalenes using catalyst of mordenite and a carrier. Gamma alumina carriers are not recognized in this application.
U.S. Pat. No. 3,915,895 issued Oct. 28, 1975, relates to disproportionation of alkyl aromatic hydrocarbons in the presence of a catalyst which comprises the hydrogen form of mordenite and a group 1-B metal. The catalyst may also contain a group VI-B metal and can additionally be admixed with eta or gamma alumina. The catalytic properties of this catalyst, however, require that the specified metal or metals be placed on the catalyst.
U.S. Pat. No. 3,888,938 issued June 10, 1975, relates to liquid phase catalytic rearrangement of dimethylnaphthalenes by reacting those materials in the presence of a mixed catalyst which contains about 70 to 95 percent by weight of the hydrogen form of mordenite which mordenite has at least 80 percent by weight of the metal cations replaced with hydrogen ions, and from 30 to 45 percent by weight of a promoter selected from the group consisting of bentonite and fuller's earth. The combination of the hydrogen form of mordenite was either bentonite or fuller's earth according to the teachings of this patent contribute to an improved isomerization process.
U.S. Pat. No. 3,798,280 relates to a process for isomerization and crystallization of dimethylnaphthalenes wherein the isomerization takes place using the hydrogen form of a mordenite which is generally in its pure form. There is no teaching or disclosure that the hydrogen from of mordenite can be mixed with any specified materials such as gamma alumina, and further more, no teaching that isomerization can be carried out in the absence of metallic components.
U.S. Pat. No. 3,851,002 issued Nov. 26, 1974, relates to a process for the isomerization of dimethylnaphthalenes in the gas phase by processing the feed materials over a silica-alumina catalyst having a specified particle size distribution.
U.S. Pat. No. 3,855,328 issued Dec. 17, 1974, relates to a process for the isomerization, transalkylation or disproportionation of alkyl naphthalene materials. Particular, alumino-silicate zeolites are used as the catalyst in such processing. The preferred zeolites have atomic ratios of aluminum to silica in the range of about one to one-tenth. A preferred zeolite is a faujasite framework structure typically referred to as Linde type "Y" molecular sieves containing a specified rare earth cation such as cerium or lanthanum.
U.S. Pat. No. 3,780,119 issued Dec. 18, 1973, relates to a process for isomerization of dimethylnaphthalenes using a mordenite catalyst which contains at its ion exchangeable sites, a metal selected from the group consisting of lanthanum, sodium, potassium, magnesium, calcium, strontium, barium, aluminum, and zinc. The metal containing mordenite material is specifically disclosed as the primary catalytic agent in the process of this patent.
In a summary review of the prior art described, it can be concluded that there is no teaching or disclosure of the unique use of the hydrogen form of mordenite dispersed in a gamma alumina matrix. The specific claimed concentration of the hydrogen form of the mordenite in the alumina is not taught nor are the benefits relating to yield and catalyst life attributed to the specified mordenite concentration recognized.